The radial distance from the pitch circle of a cogwheel or wormwheel to the crests of the teeth or ridges.

3.
Machinery.
the radial distance between the tip of a gear tooth and the pitch circle of a gear or the pitch line of a rack.Compare dedendum.
Also called addendum circle. an imaginary circle touching the tips of the teeth on a gear.

Examples:

"addendumses can be to numbers."

Origin:

addendum

Late 17th century: Latin, ‘that which is to be added’, gerundive of addere (see add).